Posted
by
timothy
on Thursday July 23, 2009 @02:10PM
from the lots-of-girls-I-know-glow-visibly dept.

An Anonymous Reader writes "The human body literally glows, emitting a visible light in extremely small quantities at levels that rise and fall with the day, scientists now reveal. Japanese researchers have shown that the body emits visible light, 1,000 times less intense than the levels to which our naked eyes are sensitive. In fact, virtually all living creatures emit very weak light, which is thought to be a byproduct of biochemical reactions involving free radicals."

They aren't, as such. What we know as a "halo" is more of a Hanna-Barbera cartoon knock-off of something that appears in a lot of early Christian art as a nimbus - a sort of glowing aura around Jesus and sometimes an accompanying Lamb. According to this wikipedia page [wikipedia.org] the concept was used earlier in a lot of other historical religious art too before becoming bastardized by pop culture's somewhat clumsy literal interpretation.

At least not to most people. Assuming that light sensitivity and light emission are independently normally distributed in the population, it's entirely possible that extremely sensitive individuals can see the light coming off the extremely bright individuals. Further, it is possible for genetically isolated populations to have gained extreme sensitivity or extreme brightness through the usual biological mechanisms, or if such traits were selected for through cultural or religious practices. Also, consider that relatively unstressed young Japanese men may not be fully activating whatever metabolism or physiology issues the light. There may be something to metabolism around "afterglow", women glowing when they're pregnant, unusual mental capacity, etc. which could easily generate 10 or 100 x the intensity observed in this study, and thus be observable by many people. (All sorts of biological processes span several orders of magnitude in concentration, intensity, energy, etc., and plenty of other bio-luminescent organisms show that the energy levels required to emit naked eye visible light are mostly not harmful to the organism.)

Whether we are consciously aware of the brightness of others, or if we do anything with that information are topics for future study.

Not that I really feel the ability to see auras would prove God or psychics or anything, but your conclusion is making an assumption that has no basis.

Just because we can see a dim light, does not mean that a bright one would blind us. It tends to be true due to the way our iris works, but even in bright indirect sunlight we can see dim directed lights, and there is no saying that the iris would filter out all of a dim directed light.

No, what I'm saying is that the proposition, "People Emit Visible Light", is a crock. I take words seriously. When they say "visible", I take it to mean "VISIBLE". If they meant to say, "people emit light in the visible part of the spectrum", then they should have said exactly that. Words have meanings.

You don't even have to assume some people are more sensitive to light, and can "see" it.

There was a study a while ago about conscious and subconscious sight. Apparently certain kinds of blindness leave subconscious vision semi in-tact, so although the person couldn't see, he could snap his eyes shut if a bug was about to hit them.

"Halos" might not even be literal halos, so much as a feeling you get when looking at someone.

Your subconscious doesn't have a lot of ways to communicate. It's limited to feelings

Usually "visible light" means "electromagnetic radiation with wavelength lying in (approximately) 380-750nm range". At least that's what they taught us in the university. Somehow, I find this definition much more logical than yours, no offense meant.

This isn't any kind of new or unpredicted phenomenon. Everything that emits heat emits some light. The chances that the wavelength of a photon emitted by a human being (while giving off normal heat) will fall within the visible spectrum is very low, but given that we emit billions and billions of photons on a regular basis, it's sure to happen every now and then. Get sensitive enough cameras, and you'll see that glow from everything that isn't at absolute zero.

No. His argument, correct but incompletely stated, is that any macroscopic object with a temperature emits a blackbody(-ish) spectrum which, since it spans the entire range of EM radiation, emits some light in the visible portion of the spectrum.

Correct. Doing a quick back of the envelope calculation a human body will emit one photon with a wavelength of 600nm every 10 seconds. If we scale that up by a factor of 1,000 that would mean the human eye would need to be capable of seeing a flux of 100 photons/second per unit solid angle. This is well below the threshold of a human eye - you'd need a photomultiplier or low temp photon counter device to pick this up. So clearly this is not the source of light.

Ah - but you are forgetting the solid angle. My rate is 100 photons/second/per steradian. I have no idea how small a rod is but probably on the 1 micrometre? (it has to be bigger that the wavelengths it detects which are 100's of nm). Hence you would have to place your retina within ~5 micrometres of the source for each rod to subtend a solid angle of 0.01 steradians to get one photon a second - which the article says that you still won't be conscious of - particularly since at this point you've rammed the

I'm curious though if the brain can be trained to pick up this information though.

Most people believe that their entire vision is in color, despite the fact that the cones detecting color are only in the center of the eye. The edges of our vision (the "corner" of our eye) only sees black and white. The brain fills in the detail so we think we see it all in color.

Likewise, if you can get the brain to NOT suppress the very rare photon events, then its possible that it could "save and correlate them" into wh

You're right that they need different energies. If you graph the energies of photons emitted due to heat radiation, they'll form your typical bell curve, with the peak of the bell curve representing and energy level corresponding with infra-red radiation. That having been said... a few standard deviations from the center, you'll see the (very rare) photons emitted that have energy levels corrosponding with visible light. This happens when enough energy concentrates (by random, highly unlikely chance) to

they'll form your typical bell curve, with the peak of the bell curve representing and energy level corresponding with infra-red radiation... This happens when enough energy concentrates (by random, highly unlikely chance) to create a photon with much higher energy than is typical for a radiating body.

So what process creates the other half of the bell-curve, the photons at a lower energy than infra-red radiation?

Read about Planck's Law [wikipedia.org]. It predicts the distribution of photons by frequency dependent on temperature. The scale is from wavelength = 0 to wavelength = inf, but the distribution is an asymmetric peak that goes to shorter wavelengths as the temperature increases. The extremely large majority of photons emitted by an object at 293K will be in the infrared, but a few will be visible, ultraviolet, and x-ray.

X-rays, hmm, so being in crowded places does increase the exposure to harmful radiation. I always knew that one should avoid crowds and now it is confirmed. That also means that, given enough people, one can demonstrate an attack using photonic means.

[tinfoilhat_hat]Makes me wonder when an overzealous politician picks it up and limits demonstrations to few people to lower exposure to radiation.[/tinfoilhat_hat]

The chance of emission at higher energies decreases exponentially. You're getting far, far, far more exposure to ionizing radiation from the naturally radioactive potassium in others' bodies than by their black-body emission.

Just to be pedantic, you'd have to move it into a colder room or it won't be distinguishable from the background emissions of everything else. The only things that could possibly be distinguishable would be things that produce their own heat, whether electrically or chemically.

The important thing here is we just discovered the solution to the energy crisis, all we need are MORE people.
Think about it; if 1 person emits light 1000 times too faint to see, that means 1000 people emit exactly enough light to see. All I need are 1000+ Chinese people willing to stand around in my hallway for a couple pennies a month and I don't need a nightlight to find my way to the pisser at 4am anymore!!!

It is definitely unpredicted by conventional theory. The visible part of the black-body radiation spectrum (which you seem to be referring to) for an object at human-body temperature is far less than 1/1000th of what is still visible. These emissions are therefore not thermal. And the is no other conventional theory that mandates such emissions.

These results are specifically about the deviation of the spectrum produced by a human from a black body, and how that varies throughout the day. For a blackbody, the number of photons coming out as visible radiation is 1/10^3000 the total number (assuming a body temperature of ~280K, the number is so tiny because visible photons fall into the exponential Wein tail of the BB distribution), so you would naÃvely predict that no human has ever emitted a visible photon. Ever.
So yes, it is something speci

See Planck's law [wikipedia.org]. The power density at a given wavelength is inversely proportional to an exponential function of the photon energy, for wavelengths short compared to the peak. For humans (37 celsius), the peak lies at about 9.3 microns. If this were thermal radiation from a blackbody spectrum, the exponent for the longest visible wavelengths would be about 66.3, corresponding to about 1.9 * 10^-20 W/m^2 of radiated power in the visible spectrum, assuming perfect emissivity. If a typical human has a surface area of 2 m^2, that's around one thermal photon every ten seconds in the visible spectrum. This is many more than 1,000 times too dim to see. The photons referred to in the article come from chemical reactions, not thermal radiation.

Yes, but you're talking about a blackbody spectrum, whereas the article is implying that this is something else (photons released by chemical reactions, not by the thermal jiggle of charge). See http://en.wikipedia.org/wiki/Biophotons [wikipedia.org]

The summary, most commenters, and largely the article itself seem to be missing the big point here

The researchers found the body glow rose and fell over the day, with its lowest point at 10 a.m. and its peak at 4 p.m., dropping gradually after that. These findings suggest there is light emission linked to our body clocks, most likely due to how our metabolic rhythms fluctuate over the course of the day...

Since this faint light is linked with the body's metabolism, this finding suggests cameras that can spot the weak emissions could help spot medical conditions

So yes, people glow, and yes, this was known previously. The point of the research is that this can be used, for studying circadian rythms and maybe identifying problems with it and metabolism. The scientist quoted is billed as a "circadian rhythm biologist," you've got to think he's probably not studying this to find out if people glow or not.

The information in the summary is thirdhand at best: whoever makes the summary makes it from an article, which in this case wasn't primary literature from the actual scientists but was AOL news or whoever "imaginova corp" is interviewing several japanese scientists about their work. AOL news seems to have misunderstood the research that they were writing about.

It was discovered in 1923 by a Russian scientist, Alexander Gurvitsh. It was re-discovered in the 70s by a German physicist named Fritz-Albert Popp. This stuff is really old, they discovered nothing new. Popp proposes that this emission is very different from typical black body radiation.

So the allegedly emitted light is 1000 fainter than what human eyes can see. Then why call it "visible", meaning viewable, seeable, ocularly pursuable (thanks Charles Dickens, Tale of Two Cities... it has been a long time since I had the pleasure of ocularly pursuing you... is Dickenesque for long time no see) ?

May be I can use this definition to claim my code is fully documented when the sole documentation is a line of comment that says, "Someday I should document this insane hack."

From wikipedia [wikipedia.org]: "The visible spectrum is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light."

The terms are a bit confusing, but the term "visible" light has nothing to do with magnitude, it only refers to light with a particular wavelength, roughly 380 to 750 nm, which our retinas happen to be sensitive to. The term visible is not meant to differentiate visible light from invisible light, but rather to differentiate these waves from radio waves, infrared, ultraviolet, X rays, microwaves, and gamma rays. So yes, even if the light cannot be seen, if it is in that particular spectrum, it is visible light.

Right on.. It would help if popular culture could just call it all EM Radiation [wikipedia.org], and call "visible light" EM Radiation in the visible spectrum, but the term radiation scares people. Maybe as an acronym, EMR and EMR-V would be less frightening. Nonetheless, it would be more technically accurate, and remove the ambiguity of the term "light".

There are two factors when considering light. The number of photons and the wavelength of each photon. In this experiment the first one makes the light they are considering faint. The wavelength of those few photons is what makes them in the visible spectrum. Or another way to look at is ultraviolet light from the sun is fairly intense outside, but we don't see it because our eyes aren't designed to detect that wavelength. The neat part, that is probably most useful, is that it detects how the metabolism is

Similar "biophoton" phenomena have been studied in the past at the International Institute of Biophysics [lifescientists.de]. It is most interesting as conventional theories do not predict such emissions.

So, since this light is directly related to biological processes, that means in theory it should be tied to mood. For instance, clinical depression is tied to a general depression of all physiological processes. So, it would stand to reason that if you're down, you would emit less light. Someone who is euphoric should look (relatively) like a lightbulb in comparison. I know in the article it says that the amount and color of light varies, I wonder if this would lead towards a mood-ring style ability to read emotions. For instance, someone who is emitting a "pensive" light spectrum, along with other biological cues like sweat, and fidgiting may be a good suspect for scrutiny.

So, since this light is directly related to biological processes, that means in theory it should be tied to mood. For instance, clinical depression is tied to a general depression of all physiological processes. So, it would stand to reason that if you're down, you would emit less light. Someone who is euphoric should look (relatively) like a lightbulb in comparison. I know in the article it says that the amount and color of light varies, I wonder if this would lead towards a mood-ring style ability to read

I'm assuming they mean that the body emits an invisible (to the human eye) amount of light in the "visible" spectrum, i.e. within the wavelength ranges that we could detect if the quantity was sufficient.

Careful analysis tells me it is absolutely necessary for the survival of the human race to investigate photon emission from women. Since cloth would interfere with measurements, experiments will have to be clothing-free, and in a dark room. Volunteers are needed, apply now. Scientific requirements show a need for women between 18 and 40 with large busts. No pay, but refreshments will be served in sufficient quantities to achieve experimental results.

I'm still applying for a grant to research this, but I'm told people also emit a scented gas! Part of my research will focus on this 'silent but deadly' scenario as it appears this scent is not always accompanied by sound.

Close. A single photon is capable of making a single cell (rod) in your retina fire. To actually perceive light, you need around 9 or 10 rods to fire at around the same time. Problem here is that only around 10% of the photons entering your eye end up striking a receptor - the rest are reflected off of the cornea, get absorbed in the vitreous humor (fluid inside the eye), or pass through the retina without striking a spot where a receptor is located.

1. The rods of the human retina can react to a single photon. However, to be consciously perceived between 5 and 10 photons must be detected within 100 milliseconds. To pick up light that's 'visible', but "1,000 times less intense than the levels to which our naked eyes are sensitive" ('Which is, of course, impossible. -- Hitchhiker's Guide) the researchers in TFA are claiming to detect small fractions of a photon (repeat HHG assertion here).

As stated, the above applies to conscious perception. A normally non-conscious perception via an alternate visual channel has been proven to exist. This 'blindsight' has been discussed here previously http://science.slashdot.org/article.pl?sid=08/12/24/2330245 [slashdot.org] . It has been shown to not only exist in the sighted, but can be trained in them so to become functional. There was a school for this in New Mexico that was written up in Co-Evolution Quarterly almost 20 years ago. In the discussion thread here, more than one person admitted to having developed or noticed having this ability.

2. The spirit of we two legged can become attuned to the spirit of the four legged, and so the hunter can find prey in darkness, and one can also avoid becoming hunted. Likewise, we can feel the spirit of the standing people (trees) and so find our way between them with surprising speed. Although it works as though it were sight, because it is a working of the spirit, the impressions received are not detected as visual images to the mind, but only to the spirit.

I've got a lot of academic training in #1. I've got some training, and have ancestors with a lot more in #2. They may be incompatible, but since no viewpoint perfectly and completely describes reality, none can be said to be the only truth. In any case, learning to use dark sight doesn't require believing either.

You're trying to redefine the word visible. It's within the visible spectrum. Which means that while we have one ingredient to the recipe, we're still lacking enough quantity. This makes it invisible. Same goes with your star example.

And you're playing a semantic trick where you take a word with multiple definitions, and change the definition you're using from the one that was clearly implied by the original context.

In the headline "People Emit Visible Light", "Visible" means "in the visible portion of the spectrum". "Visible Light", especially in a scientific context, usually means "light which is in the visible portion of the spectrum".

In the headline "People Emit Visible Light", "Visible" means "in the visible portion of the spectrum".

I don't think that's obvious... well, other than the fact that they don't emit visible light by the definition I'd normally assume was meant. Since I can look around and see that they don't...

If I told you that a lightbulb emitted an "audible" sound, you'd assume I meant you could hear it. It wouldn't make sense to claim that if it was emitting sound at 120 hertz (an "audible" frequency) but at a volume far too low to be perceived by the human ear.

I don't think that's obvious... well, other than the fact that they don't emit visible light by the definition I'd normally assume was meant. Since I can look around and see that they don't...

It's extremely obvious if you're aware of the meaning of "visible light" in a scientific context. Anytime you see the phrase "visible light" in the same sentence as "scientists say" or "researchers have shown", then it is nearly 100% certain that this is the intended meaning. The clincher would be if you consider the

Whatever researchers may use it to mean, the majority of people will probably be inclined to use the dictionary definition, and the most common one, if you don't clarify:

1 a: capable of being seen <stars visible to the naked eye> b: situated in the region of the electromagnetic spectrum perceptible to human vision < visible light>

Wait. You're telling me that the majority of people will use definition 1a, and only 1a, without even considering 1b, even though 1b specifically and directly refers to the exact phrase being used -- "visible light"?

You're telling me that the majority of English speaking people do not ever consider the multiple definitions that nearly every word in our language has, and choose based on contextual clues what the most likely intended meaning is? I don't buy that for a second. You know why? Because just now, without even thinking about it, you automatically processed the word "buy" and based on the contextual clues chose meaning number 5 [merriam-webster.com].

This has nothing to do with people choosing the first definition from a dictionary as opposed to the second, because nobody was looking in a dictionary. This has to do with people not knowing a scientific term so common and non-obscure it's definition 1b in said dictionary.

So basically, if you mean "light in the visible spectrum", just say that. "Visible light" will be interpreted by most people according to the 1a definition of "visible", not the 1b definition. It comes first because it's common...

Okay, once again I'm surprised, and again I admit it must just be the fault of my perception.

I would never have guessed that people who have no idea what "visible light" means would find the phrase "light in the visible spectrum", or even just "spectrum" meaningful. I wouldn't have thought those people even knew that the stuff outside the visible spectrum was light. So you're telling me that people know that the colors in a rainbow and X-rays and radio waves are all the same thing, they're all light, but at the same time have no idea what "visible light" could mean? I really never would have expected that.

I guess this illustrates one of the difficulties of writing about technical material for a layman audience -- remembering what it was like to be a layman, and thus what a layman would understand, when that could have been a long time ago. As far as I can remember, I learned about the EM radiation spectrum that includes X-rays, radio waves, infrared, and the light our eyes are sensitive to along with the phrase "visible light" to describe the latter section of the spectrum in a single class session in high school physics. So it would never have occurred to me that you could expect your audience to know one and not the other.

And you're assuming that Slashdot headlines are viewed as Scientific forum (capitalization used to emphasize your bias). Slashdot is not a scientific forum, but a nerd-emphasised general forum. Thus the common or vernacular definition should always be used, and the editors should remember that headlines are summaries of the article and stand alone frequently without further explanation.

And you're assuming that Slashdot headlines are viewed as Scientific forum (capitalization used to emphasize your bias).

When the sentence containing the phrase in question also includes the phrase "scientists reveal" and the next sentence includes "researchers show", then it is probably safe to interpret it in a scientific context.

I will admit that I am biased towards thinking that most slashdotters would have attended and been interested enough to pay attention to high school or entry-level college physic

Saying that the human eye can perceive 5 photons is missing a bunch of units. The time portion is very important, as well as how spread out they are over the eye. In the pictures in the article, the light emitted from the face peaked out at around 3000 photons per second per square centimeter. If humans need 3,000,000 photons / s*cm^2 to perceive light, then you just need to focus the beam tightly over a short stretch of time - if you send those 5 photons in a single ms over.17 mm^2, you'll get approxim

The visible spectrum. I agree that the headline is misleading, but I get what they meant.

Infrared, for instance, is invisible no matter how intense it is. For example, the infrared light from the LED on your TV remote is perfectly invisible to your eye, but a digital camera (which certainly isn't intended to be "incredibly sensitive") will pick it up just fine. Try it!